RU2613006C2 - Composition welding wire - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: composition welding wire for repair by fusible welding of the gas turbine engine parts made of heat-resisting alloys based on nickel, cobalt or iron, comprises a core and a surface layer applied and connected to it, containing boron and/or silicon. The total content of boron and/or silicon in the composition welding wire is calculated by formula

where C_∑ is the total content of boron and/or silicon in the welding wire; D' is the diameter of the welding wire; C_SL is the content of boron and/or silicon in the surface layer; T is the thickness of the surface layer, wherein C_∑ is 0.1-10 wt %.

EFFECT: prevention of the cracking in the heat affected zone due to the fusible welding and argonarc welding of the dispersion-hardened heat-resisting alloys.

17 cl, 13 dwg, 1 tbl, 6 ex

Description

The invention relates to welding and, in particular, to filler materials for fusion welding, which can be used to repair parts of gas turbine engines made of heat-resistant alloys based on nickel, cobalt and iron using argon-arc welding with a non-consumable electrode, laser, plasma and microplasma manual and automatic welding.

Several generations of heat-resistant nickel and cobalt-based alloys have been developed for gas turbine engines in recent decades. However, despite the unique mechanical properties and high oxidation resistance, engine parts made of dispersion hardening heat-resistant alloys are still susceptible to cracking due to thermal fatigue, high-temperature oxidation and corrosion, as well as erosion.

To repair parts of gas turbine engines with significant damage, Liburdi Engineering Ltd. developed and patented the Liburdi Powder Metallurgy (LPM ™) powder metallurgy process, first described in US Pat. No. 5,156,321 in 1992.

The LPM ™ process is based on applying a paste obtained from Mar M-247, Inconel 738 powders and other heat-resistant alloys and an organic binder to the repaired area and sintering the powder at temperatures exceeding 1000 ° C to obtain a porous material that is metallurgically bonded to the substrate followed by impregnation of the porous material with solder based on nickel or cobalt, holding at high temperature, ensuring metallurgical interaction of the molten solder with heat-resistant powder, which after cooling and dations with the parent metal to form a repaired area materials with high mechanical properties and resistance to oxidation.

General Electric developed and implemented a similar process called Activated Diffusion Healing (ADH), described in Wayne A. Demo, Stephen Ferrigno, David Budinger, and Eric Huron "Improving Repair Quality of Turbine Nozzles Using SA650 Braze Alloy ", Superalloys 2000, Edited by TM Pollock, R.D. Kissinger, R.R. Bowman, KA. Green, M. McLean, S. Olson, and J.J. Schim, TM.5, The Minerals, Metals & Materials Society, 2000, pp. 713-720.

When repairing according to the ADH process, a paste-like mixture of heat-resistant metal powder, solder, which has a lower melting point due to the addition of boron (B) and silicon (Si), and an organic binder (hereinafter ADH paste) is applied to the area to be repaired.

ADH materials have a low melting point, mainly due to the use of boron. The level of boron is balanced between the minimum necessary for impregnating a porous material and healing cracks, on the one hand, and the negative effect of boron on mechanical properties, on the other hand. In both processes (ADH and LPM ™), the repaired area contains a significant amount of fusible material, which makes it extremely difficult to carry out subsequent repairs or repair any defects using fusion welding using standard filler materials. As a result, to repair even minor defects in LPM ™ and ADH, cycles must be repeated, which increases the cost of repair and reduces the properties of the starting material due to excessive boron diffusion.

Joe Liburdi et al. Reported some progress in using Inconel 625 filler wire argon arc welding to repair LPM ™ materials in the Novel Approaches to the Repair of Vane Segments article at the Cincinnati International Gas Turbine and Aircraft Congress and Exhibition , Ohio, May 24-27, 1993, published by the American Society of Mechanical Engineers, 93-GT-230. However, the practical application of this method is limited due to the high melting point of Inconel 625, which leads to the melting of LPM ™ materials in the fusion zone.

In addition, the use of fusion welding to repair engine parts made of Inconel 738, Inconel 713, Rene 77 and other heat-resistant alloys with a total aluminum and titanium content exceeding 8% leads to cracking of the heat-affected zone (HAZ).

As follows from the article by Banerjee K., Richards NL, and Chaturvedi M.S. "Effect of Filler Alloys on Heat Affected Zone Cracking in Pre-weld Heat Treated IN-738 LC Gas-Tungsten-Arc Welds", Metallurgical and Materials Transactions, Volume 36A, July 2005, pp. 1881-1890, which presents the results of a study of the influence of Hastelloy C-263 nickel-based welding wire manufactured according to technical specifications on Aerospace Materials Specification AMS 5966 and containing 0.4% Si, among other alloying elements, and welding silicon-boron-free nickel-based wires, AMS 5832 (also known as Inconel 718), AMS 5800 (Rene 41), AMS 5675 (FM-92) having different melting points and chemical compositions, attempts to obtain welds without cracks when welding Inconel 738 using standard filler materials the drags were unsuccessful. According to the data of this work, it was shown that all samples obtained using the aforementioned filler materials were subjected to intense cracking in the HAZ due to the fact that the temperature range of the crystallization of the weld pool exceeded the melting temperature of the eutectic along the grain boundaries. Overheating of the HAZ along the fusion line caused segregation cracking of the base metal along the grain boundaries.

To verify the above results, the authors of the present invention during the current development evaluated the weldability of Inconel 738 using another group of welding materials, including standard welding wires AMS 5786 (Hastelloy W) and AMS 5798 (Hastelloy X) based on nickel, which were included along with others alloying elements up to 1% Si by weight, as well as using a Haynes HR-160 nickel-based welding wire with a silicon content of 2.75% by weight and other welding wires in which the volumetric silicon content ranged from 0.05% to 2% by m sse, like an alloy described in U.S. Patent 2,515,185.

Regardless of the chemical composition, in all welds obtained using standard welding wires, intergranular microcracks were found in the HAZ along the fusion line between the base metal and the weld. The formation of cracks in the HAZ of the Inconel 738 alloy was associated with the melting of low-temperature eutectics, carbides, and other precipitates along the grain boundaries during welding, followed by the propagation of cracks due to the continuously increasing level of residual welding tensile stresses in the HAZ during crystallization and cooling of the weld.

The low content of low-temperature eutectics and rapid cooling of the weld metal was sufficient for crack nucleation, but insufficient to heal these cracks with molten eutectic material, as shown in the publication by Alexandrov V.T., Hope A.T., Sowards J.W., Lippold J.C., and McCracken S.S. Weldability Studies of High-Cr, Ni-base Filler Metals for Power Generation Applications, Welding in the World, Vol. 55, n. 3/4, pp. 65-76, 2011 (Doc. IIW-2111, ex Doc. IX-2313-09).

The high melting points of standard cobalt-based welding consumables with a total Si content of up to 2.75%, which exceeded the Inconel 738 melting start temperature, increased overheating and increased cracking in the HAZ. Heat treatment of welds led to additional cracking. Some cracks extended into the welds.

Therefore, at present, only the preheating of Inconel 738, Inconel 713, GDT 111, GDT 222, Rene 80 and other dispersion hardening polycrystalline alloys, as well as alloys obtained by directional crystallization, heat-resistant alloys with a high content of gamma-prim phase, as well as Rene 80, CMSX 4, CMSX 10, Rene N5 and other single-crystal materials, up to temperatures exceeding 900 ° C, allows welds to be made without cracks. Welding methods using preheating are described in US Pat. Nos. 5,897,801, 6,659,332 and Canada 1,207,137. However, preheating parts before welding increases the cost of repairs and reduces labor productivity.

In addition to standard solid-section welding wires, various composite wires are also known. Composite welding wires with a coating or surface layer are the most common. For example, the composite welding wire described in US Pat. No. 5,596,546 contains 1.5-2.5% B, 2-5% Al, 2-4% Ta, 14-17% Cr, 8-12% Co and Ni mixed to balance. Boron is used as a melting point depressant, which ensures welding of products made from cobalt-based alloys. However, boron reduces the ductility of cobalt, nickel and iron alloys. Therefore, this patent discloses the manufacture of such a filler wire by sintering powders. For practical application, this process is expensive and time consuming.

Flux-cored hollow and powder welding wires and solid wires described in the AMS Handbook, Brazing and Soldering Handbook, Welding, Brazing and Soldering, Volume 6, pp. 719, as well as the patents of France 2746046, Canada 2442335 and China 1408501 also apply to composite filler materials for general purposes. Flux-cored flux-cored welding wires contain a metal sheath, which is filled with various slag-forming materials, arc stabilizers, reducing agents, and metal powders. Composite wire base can be made from a variety of powders using high-performance processes. Unfortunately, the diameter of these filler materials is from 4 to 8 mm, which does not allow them to be used for the repair and manufacture of elements of gas turbine engines with wall thicknesses from 1 to 3 mm.

The bimetal composite welding wire according to Russian patent 2122908 has a good metallurgical bond between the base and the sheath, but it can be made by drawing using only materials with high ductility, such as copper and corrosion-resistant steel.

Composite copper-coated welding wires described in Japanese Patents 2007331006, 2006281315, 62199287 and Korea 20090040856 have different chemical compositions and are available on the world market. However, copper significantly reduces the operating temperature of welded joints of heat-resistant nickel-based alloys. Therefore, they cannot be used to repair elements of gas turbine engines.

Filler wires coated with silver and copper according to Chinese patent 1822246 are also not suitable for welding elements of gas turbine engines due to the specifics of the metallurgical interaction of silver with heat-resistant alloys based on nickel and cobalt.

The titanium coating of the wire according to Chinese patents 101407004, 201357293 and Japan 2007245185 is not effective enough to lower the melting temperature of nickel-based filler materials.

Coating the welding wire with active substances, such as MnCl ₂ , CaCl ₂ , MnO ₂ , and ZnO according to Chinese patent 101244489, is not effective in preventing crack formation in the HAZ of dispersion hardening heat-resistant alloys.

Composite welding wires made according to Chinese patents 1822246 and Russia 2415742, 2294272 have internal and external coatings containing activating fluxes, designed to reduce hygroscopicity. These composite wires may also contain a metal coating. However, these filler wires do not allow providing defect-free welds when welding dispersion hardening heat-resistant alloys based on nickel and cobalt due to the high melting temperature and overheating of the heat affected zone, since hygroscopic components do not reduce the melting temperature of the filler wire.

Thus, due to technological difficulties in the manufacture and use of known filler wires containing boron and silicon in the required quantities, argon-arc welding of heat-resistant nickel alloys without preliminary heating is difficult and in many cases practically impossible.

Based on the foregoing, there is an urgent need to develop a new filler material for fusion welding and argon-arc soldering of precipitation hardening heat-resistant alloys that are prone to cracking HAZ, as well as for repairing turbine engine parts that had previously been repaired using high-temperature brazing, LPM ™ or ADH.

The purpose of the invention is achieved in that the composite welding wire contains a ductile metal base (core) made of alloys based on iron, nickel or cobalt, and a surface layer based on boron, silicon or boron with silicon with a total content of boron and silicon in the welding wire of approximately 0.1-10% by weight, and the total content of boron and silicon in the wire is controlled by the thickness of the coating and the content of boron and silicon in this coating.

As a result of the experiments, it was found that a lower melting temperature of these filler materials reduces HAZ cracking, and the expansion of the crystallization temperature range leads to self-healing of the resulting cracks due to the presence of a large number of interdendritic eutectics with a low crystallization temperature.

In addition, alloying filler wires using boron and silicon in the optimal concentration range did not reduce the ductility of the welds, which made it possible to use these materials for surfacing the intermediate layers before the final application of high-strength materials with low ductility during the restoration of assemblies and parts made of high-strength brittle materials.

The composite filler wire described in the present invention can be obtained by combining a standard high-tech cold or hot drawing of a plastic metal base with the subsequent application of the required amount of boron, silicon or both of these elements in the form of various coatings on the surface of this base.

Previous attempts to produce a filler wire with a high content of boron and silicon were unsuccessful due to a sharp decrease in ductility caused by additives of boron and silicon. As a result, filler wires with a high content of boron and silicon could be made only by casting or sintering, which is uneconomical in industrial production.

The composite filler wires described in the present invention can be obtained by applying paint containing boron and silicon, or by various spraying methods on standard welding wires, followed by heat treatment. The use of standard welding wires reduces production costs. Therefore, the developed method provides a low cost of manufacturing filler wire and high productivity of the process.

Surface alloying of the metal base with boron and silicon lowers the melting point of filler materials and increases the crystallization interval of the weld pool.

The tensile strength of welds obtained using composite welding wires modified with boron and silicon, often exceeds the strength of welds obtained using standard materials at a temperature of 982 ° C (1800 ° F).

Using the developed welding wire for argon-arc welding of the Inconel 738 alloy eliminated the formation of cracks in the HAZ. It was also possible to significantly reduce the cost of repairing various parts of gas turbine engines.

According to another embodiment of the invention, the filler wire may contain a transition layer between the plastic metal base and the coating, while the content of depressants of the melting temperature gradually decreases from the maximum on the outer surface of the coating to the initial level of these elements in the material of the wire.

Hollow filler wires with a diameter exceeding 4 mm may also contain melting point depressants deposited on the inner surface.

In accordance with another embodiment of the invention, hollow flux-cored filler wires may contain melting point depressants, powder materials made of filler wire material such as Ni, Co, Fe, as well as alloying elements selected from the group of elements Al, Ti, Zr, Hf , V, Nb, Ta, Cr, Mo, W, Cu, Y, Re, C, N.

A method of manufacturing a composite filler wire includes preparing a metal base, applying a surface layer with melting point depressants selected from boron and silicon, using one of the following processes: applying a suspension and dyes, boronation, electrostatic powder spraying, liquid boronation, chemical boronization, electrochemical boration, diffusion boronation in the solid phase, chemical vapor deposition, physical vapor deposition , electron beam spraying and electron beam physical vapor deposition, so that the total content of boron and silicon in the composite welding wire is from 0.1% to 10% by weight and the binding of the surface layer to the metal base.

In FIG. 1 shows a cross section of a composite welding wire containing a ductile metal base (core) in the form of a wire 100, the outer surface layer 102 of which is enriched with depressants of the melting temperature, and the transition layer 103, while the outer diameter of the wire is' D '112, and 110 is the thickness' T 'of the outer surface layer 102.

In FIG. 2 is a cross-sectional view of a flux-cored composite filler wire 200 with a filler powder that contains a ductile metal base in the form of a hollow wire 201 with an outer surface layer 202 enriched with melting point depressants, a coaxial hole 204, an inner surface layer 205 with melting point depressants, and a filler 206, which fills the hollow portion of the wire.

In FIG. 3 is a cross-sectional micrograph of a nickel-based composite welding wire containing a boron-enriched surface layer obtained by electrochemical boronation.

In FIG. 4 is a cross-sectional micrograph of a nickel-based composite welding wire with a boron-enriched surface layer obtained by boronation.

In FIG. 5 is a cross-sectional micrograph of a nickel-based composite welding wire with a boron-enriched surface layer (a) and a silicon-enriched surface layer (b) obtained by applying a boron and silicon-based paint coating on the wire surface, respectively, followed by vacuum heat treatment at a temperature of 1200 ° FROM.

In FIG. Figure 6 shows a plate made of stainless steel 304 with a surface LPM ™ nickel-based layer prepared in accordance with US Pat. No. 5,156,321.

In FIG. 7 shows the same sample after argon-arc surfacing using boron-modified composite welding wire A, the chemical composition of which is given in the examples of surfacing on LPM ™.

In FIG. 8 is a micrograph of the sample shown in FIG. 7.

In FIG. 9 is a photomicrograph of the fusion zone between the LPM ™ coating and the weld metal obtained by argon-arc surfacing using a boron modified composite welding wire 'A', the chemical composition of which is given in the welding examples.

In FIG. 10 is a photomicrograph of welds obtained on an LPM ™ coating using a boron-modified composite 'B' welding wire with the chemical composition shown in the examples.

In FIG. 11 shows welds obtained on an Inconel 738 alloy using a boron-modified composite 'B' welding wire with the chemical composition shown in the examples.

In FIG. 12 is a photomicrograph of a weld obtained using a silicon-modified composite 'C' welding wire with the chemical composition shown in the examples relating to welding of Rene 77 alloy.

In FIG. 13 shows a section of a composite welding wire with a surface layer containing 40% boron, and a welding rod at the bottom of the photograph with a surface layer containing 12% boron and a bundle of polyester.

The present invention is a composite welding wire or rod for fusion welding 100 shown in FIG. one.

Composite welding wire 100, with the required chemical composition, is mainly intended for repairing parts of gas turbine engines made of heat-resistant alloys based on polycrystalline alloys Ni, Co and Fe, as well as alloys obtained by directional crystallization and single crystals, which were previously repaired using ADH, LPM ™ or brazing, as well as heat-resistant alloys, which are prone to cracking in the HAZ zone when welding using standard welding materials .

Composite welding wire 100 comprises a plastic wire base (core) 101 shown in FIG. 1, obtained, for example, by hot or cold drawing from standard or custom-made plastic alloys based on nickel, cobalt and iron having the necessary chemical composition. Composite welding wire 100 also contains a surface layer 102 enriched with melting point depressants such as boron, silicon, or a combination of these two chemical elements. Depending on the manufacturing process, the composite welding wire may comprise a transition layer 103.

In FIG. 1 'T' represents the total thickness of the coating with the thickness of the intermediate, usually diffusion, layer 103. The diameter of the composite welding wire, including the surface layer or coating 'D', is designated 112.

In FIG. 2 is a cross-sectional view of a flux-cored composite welding wire 200 that contains a plastic hollow base 201 with an outer surface layer 202 enriched with melting point depressants, a coaxial hole 204, an inner coating 205 containing melting point depressants, and a powder filler 206.

For the manufacture of composite welding wires for welding and repairing engine parts made of heat-resistant alloys containing ADH, LPM ™ and soldered joints, standard welding wires based on iron, nickel and cobalt alloys can be used along with wires made from special alloys.

The following describes several examples of applying boron coatings 102 and 202 of the required thickness shown in FIG. 1 and 2.

For example, a suspension prepared from a mixture of finely divided boron with a volatile solvent, such as alcohol, or methanol, or water, is applied to the surface of the wire base with a brush, spray or immersion followed by heat treatment to fix the paint on a wire base. To improve adhesion, the suspension may also contain an organic binder, which is fully or partially disintegrated either in the heat treatment process or in the welding process. The most effective is electrostatic powder spraying.

Boron-containing coatings can be applied by liquid boronation methods, in which a metal base made of standard wire is immersed in a salt bath at high temperatures similar to electrochemical boronation or diffusion boronation in solid powder mixtures.

Gas boronation in mixtures of boron-containing gases, for example, В ₂ Н ₂ -Н ₂ , can also be used for the industrial manufacture of composite welding wire.

Plasma boronation, which also uses boron-rich gases, can reduce the temperature of the composite welding wire manufacturing process.

Fluidized bed boring, in which special powders are used in combination with oxygen-free gases such as hydrogen, nitrogen and mixtures thereof, can also be used to make a composite welding wire.

Other methods of manufacturing a composite welding wire with boron-containing coatings are boronation of the wire base by: chemical vapor deposition, in which boron atoms diffuse into the base, forming intermetallic compounds on the surface of the wire bases; physical vapor deposition, in which the boron-rich material is vaporized using an electric arc in vacuum at a working pressure of 10 ^-2 torr or less; electron beam deposition from the vapor phase, which is similar to the process of physical vapor deposition, but the heating and evaporation of the atomized material is carried out by means of an electron beam; as well as electron beam spraying.

Paint and electrolytic boronation, as well as electrostatic powder spraying, are the most economical for the production of composite welding materials by the proposed method.

The required coating thickness depends on the diameter of the wire billet and the required concentration of depressants of the melting temperature, boron and silicon in the welding wire.

The content of boron, silicon or boron with silicon in the surface layer and the thickness of this layer should provide a total content of depressants of the melting temperature in the composite filler wire in the range of 0.1-10%, in order to reduce the melting temperature of this welding wire and prevent cracking in LPM ™, ADH, as well as Inconel 713, Inconel 738, Rene 77 alloys and other heat-resistant alloys with a high content of gamma-prim (γ ') phase during their welding and surfacing.

The total content of melting point depressants in the composite welding wire depends on the diameter of the wire, the thickness of the surface layer or coating and the content of the melting point depressant in the coating or surface layer, which can be calculated using the following equation:

where C _∑ is the total content of melting point depressants in the filler wire;

D 'is the diameter of the welding wire;

C _SL is the depressant content of the melting temperature in the coating or surface layer;

T is the thickness of the surface layer or coating.

After drying, the filler wire or bar coated with boron, silicon or boron silicon is subjected to heat treatment in a protective gas environment (argon, helium or hydrogen) or in vacuum at a temperature above 900 ° C, but below the melting temperature of the wire base material . The heat treatment temperature can be selected using standard reference data for each type of alloy. However, the best results were achieved by heat treatment in the temperature range 1180-1205 ° C. During heat treatment, boron diffuses into the wire, forming a strong bond with the base, and organic additives in the form of a binder decompose and are removed from the surface layer in the form of gases.

As shown in FIG. 4 and 5, heat treatment of welding wires within this temperature range leads to the formation of a diffusion layer with a high content of boron with a thickness of 'T' from 75 μm to 111 μm, including a transition layer 103. The content of boron decreases from the maximum on the surface to zero or to the initial content boron in the source material.

An increase in the time of boronation from 2 to 6 hours increases the thickness of the borated layer to 140-250 microns. These results are similar to those previously published in X. Dong et al, "Microstructure and Properties of Boronizing Layer of Fe-based Powder Metallurgy Compacts Prepared by Boronizing and Sintering Simultaneously", Science of Sintering, 41 (2009) 199-207 the process of boronation to the depth of the borated layer.

Coatings or surface layers containing boron and silicon have a good adhesive and diffusion bond with the wire base. The thickness of the borated layer depends on the time and temperature of the heat treatment. During heat treatment, boron diffuses into the substrate through the surface of the wire, forming a so-called diffusion coating, which has an excellent metallurgical bond with the substrate, which ensures their convenient use in welding.

In accordance with another variant of the proposed method for manufacturing a composite welding wire, the formation of the outer surface layer containing boron is performed using an electrochemical process in which a wire preform with the desired chemical composition is immersed in molten boric acid at a temperature of approximately 950 ° C. During boronation, boric acid dissociates, releasing boron atoms, which diffuse into the surface layer of the wire, forming Ni ₂ B and other borides. During heat treatment after boronation, metastable borides of Ni ₂ B are converted to stable compounds of Ni ₃ B. The separation of borides from boron-enriched solid solutions and phases containing up to 10% boron also occurs on the surface of the composite welding material and along grain boundaries. It was experimentally found that during electrochemical boronization, followed by subsequent heat treatment in the temperature range 900-1000 ° C, a relatively thin layer of boride is formed on the surface of the filler wires. The thickness of the borated layer shown in FIG. 3 and 4 is approximately 75 microns.

According to another variant of the developed method, the outer surface layer containing melting point depressants is obtained by diffusion boronation in Ekabor ™ boron powders or a similar powder containing 90% SiC, 5% B ₄ C, 5% KBF ₄ . During diffusion boronation using powdered materials such as B ₄ C, boron carbide decomposes into boron and carbon, allowing the boron to diffuse into the wire. Plastic wire preforms are placed in contact with Ekabor ™ powder, and then heated to a temperature of 820 ° C to 980 ° C in a protective argon atmosphere and kept in the optimal temperature range, which is chosen experimentally for each material of the wire base, as well as the required thickness of the surface layer . After a diffusion and cooling cycle, excess Ekabor ™ powder is removed using a stainless steel soft wire brush or other method of cleaning the welding wire.

Silicon does not have the same diffusion coefficient as boron. Therefore, the most effective way to manufacture a composite filler wire with a silicon-based coating is to paint and varnish coatings with a brush, spraying or immersing the workpieces in suspensions containing finely dispersed Si powder, organic binders and solvents, followed by diffusion heat treatment at a temperature of 1100-1200 ° С.

In another embodiment of the developed method, the coating of boron, silicon or boron with silicon is carried out using electrostatic spraying, also known as electrostatic painting. Powders for electrostatic coatings or dyes are made on the basis of fine powders of boron and silicon and polymeric, for example, acrylic materials, followed by heat treatment of this wire at temperatures from 140 ° C to 200 ° C, which improves the adhesion of these coatings to the substrate and gives the coatings the necessary strength and wear resistance. An example of such a wire is shown in FIG. 13. The welding wire obtained by electrostatic powder spraying can be used for manual and automatic welding of nickel and cobalt-based alloys that are not sensitive to hydrocarbons or for which additional alloying of welds with carbon is a significant advantage, for example, for carbide surfacing, which increase wear resistance . During welding, organic binders decompose, releasing boron and silicon, which are absorbed by the weld pool.

As an example of various manufacturing options for composite welding wires, coatings based on powders of boron, silicon and boron with silicon with a purity of 99% and a particle size of 1-5 microns and organic binders were used. Coatings were applied by brush and electrostatic spraying of powders to standard welding wires AMS 5837, AMS 5839, AMS 5801, Rene 80 and Rene 142 with a diameter of 1.0-1.5 mm, where AMS stands for “Aerospace Material Specifications” Specification))). The new designation of composite wires and the total content of alloying elements in these wires as a percentage by weight are presented below:

composite welding wire 'A' (made from AMS 5837 wire), contains: 20-22% Cr, 9-11% Mo, 3.5-4% Nb, 0.5-0.8% B, Ni and impurities - rest;

'B' composite welding wire (made from AMS 5839 wire) contains: 21-23% Cr, 1.5-2.5% Mo, 13-15% W, 0.3-0.5% A1, 1.5 -1.8% Si, 0.5-0.8% Mn, Ni and impurities - the rest;

composite welding wire 'C' (made from AMS 5801 wire) contains: 21-23% Cr, 21-23% Ni, 14-15% W, 0.05-0.08% La, 0.5-0.8 % B, 1.2-1.5% Si, Co and impurities - the rest;

'D' composite welding wire (made from AMS 5694 wire) contains: 23-25% Cr, 11-13% Ni, 1-2.5% B, 1.2-1.5% Si, Fe and impurities - the rest .

After drying, filler wires were heat-treated in a vacuum of 10 ^-4 Torr or lower in the temperature range from 1120 ° C to 1205 ° C with a holding time of two hours, followed by cooling in a vacuum oven.

Visual and metallographic analysis of the obtained composite filler wires confirmed the formation of a continuous boron layer with a thickness ranging from 105 microns to 175 microns. A typical microstructure of a welding wire obtained using this method is shown in FIG. 4 and 5.

To demonstrate the method of manufacturing composite welding wires by dyeing, 100 grams of boron powder with a purity of 99% was mixed with 100 grams of an acrylic-based binder and 150 grams of Dowanol ™ brand solvent. The mixture was thoroughly mixed to obtain a uniform suspension with the viscosity necessary for brush application. The suspension was applied to welding wires with a diameter of 1 mm with a brush in two layers and left to dry for two hours. During the drying process, Dowanol ™ evaporated to form a dense coating based on boron and acrylic, perfectly adhered to the wire base.

In another example of the manufacture of composite welding wires, 60 grams of acrylic were dissolved in 150 grams of pure acetone. This solution was intensively mixed until the acrylic was completely dissolved, followed by the addition of 40 grams of Si powder with a particle size of 1 μm to 5 μm. Stirring was continued with the introduction, if necessary, of an additional amount of acetone to obtain the viscosity necessary for applying the paintwork with a brush. Next, the wire blanks were stained using a soft brush and left to air dry at ambient temperature for 15-30 minutes. After evaporation of acetone, Si and acrylic formed a uniform surface layer with good adhesion to the wire base, which ensured the required filler wire supply to the weld pool without breaking the silicon-based surface layer.

Composite welding wires in coils with acrylic powder coating containing 10-45% boa, the rest is acrylic, were obtained using electrostatic spraying, also known as electrostatic painting, followed by polymerization of the coating in a furnace at a temperature of 140-160 ° C. The thickness of the surface layer ranged from 15 μm to 500 μm. Standard electrostatic powder spraying equipment was used to make this filler wire. A fragment of a spiral welding wire for automatic argon-arc welding is shown in FIG. 13.

To demonstrate argon-arc welding and brazing using the developed composite welding wires, experiments were performed on samples containing substrates made of corrosion-resistant steel 304 and Inconel 738 alloy with 1–4 mm thick LPM ™ coating. Shown in FIG. 8. LPM ™ coatings were obtained by high temperature brazing in a vacuum furnace using AMS 4777 alloy solder.

The manual argon arc welding process using the developed composite filler wires with a diameter of 1-1.5 mm was performed using a standard SK welding torch with a non-consumable tungsten electrode with a diameter of 1/16 inch. The welding current was controlled in the range of 20-40A, the arc voltage varied from 9V to 12V depending on the distance between the tungsten electrode and the samples. After the formation of the weld pool, further heating and melting of the LPM ™ material was performed through a layer of molten filler material, which prevented the overheating and cracking of the latter.

Welding example 1.

To create high welding stresses and initiate cracking in the coating of LPM ™ material, which was deposited on a plate of corrosion-resistant steel 304, straight and annular coaxial V-grooves were made with a depth of 1-1.5 mm, as shown in FIG. . 6, similarly to the testing of standard materials with low ductility for susceptibility to cracking. The grooves were surfaced using argon-arc welding and composite filler wires A and B. As shown in FIG. 7, surfacing did not lead to cracking of the surface of the LPM ™ material. The metallographic analysis also did not reveal cracking of the LPM ™ material in the post-weld state, as shown in FIG. 8. The depth of the HAZ was 7-8 μm. The heat treatment of surfacing after welding at a temperature of 1120 ° C also did not lead to the formation of cracks in the HAZ, as shown in FIG. 9.

Welding Example 2.

Argon arc welding was performed on a high pressure vane containing a layer of LPM ™ material to establish the suitability of the developed composite filler materials for the repair of LPM ™ materials and the heat-resistant alloy Inconel 738 with dispersion hardening. Metallographic analysis did not reveal cracks in the surfacing of both HAZ LPM ™ and the base metal in the initial state and after heat treatment at a temperature of 1120 ° C, as shown in FIG. eleven.

Welding Example 3.

Successful repair of cracks on nozzle blades made of Rene 77 alloy was carried out using manual argon-arc welding, composite 'C' welding wire and welding current of 50-60A. Non-destructive quality control and metallographic analysis did not detect cracks along the fusion zone in the “after welding” state and after heat treatment at a temperature of 1205 ° C for two (2) hours, followed by cooling in argon. A typical weld structure is shown in FIG. 12.

Welding Example 4.

Successful argon-arc surfacing on corrosion-resistant steel 304 was performed using composite filler wire 'D' at welding currents of 40-50A to demonstrate the applicability of composite filler wires for welding and surfacing of steels and alloys based on iron. Non-destructive quality control and metallographic analysis did not detect cracks along the fusion zone and surfacing in the state "after welding".

Welding Examples 5 and 6.

Composite filler wires 'E' and 'F' were made by applying a suspension of silicon based on standard welding wires Rene 80 and Rene 142, followed by their heat treatment at a temperature of 1200 ° C for two hours in vacuum. After heat treatment, composite filler wires contained the following chemical elements:

- composite welding wire 'E': 9.5% by mass of Co, 14% by mass of Cr, 4% by mass of W, 4% by mass of Mo, 3% by mass of Al, 3.3% by mass of Ta, 0, 06% by mass of Zr, 0.17% by mass of C, 5% by mass of Ti, 0.3% by mass of Fe, 2.1% by mass of Si, Ni and impurities - the rest;

- composite welding wire 'F': 12% by mass of Co, 6.8% by mass of Cr, 4.9% by mass of W, 1.5% by mass of Mo, 6.1% by mass of Al, 6.3% by mass Ta, 0.02% by mass Zr, 0.02% by mass C, 2.8% by mass Re, 1.0% by mass Ti, 1.2% by mass Hf, 0.2% by mass Mn, 1.88% by weight of Si, Ni and impurities - the rest.

Filler wires 'E' and 'F' in the form of rods were used for manual argon-arc butt welding of rods from Inconel 738 and Mar M002 with a diameter of 0.5 inches. Welding was carried out at ambient temperature, without preheating. The welding parameters were selected experimentally in such a way as to ensure the content of the base metal in the joints is not more than 40%.

The welded joints were subjected to two-stage standard aging in vacuum at a temperature of 1120 ° C for two hours, followed by exposure at 845 ° C for twenty-four hours and cooling in argon.

Standard round specimens were fabricated and subjected to tensile tests at 982 ° C according to ASTM E21. Testing the samples for long-term strength was carried out at a temperature of 982 ° C and at a voltage of 22 thousand pounds per square. inch, according to the US standard for mechanical testing of samples ASTM E-139. Before mechanical testing, samples of welded joints were subjected to radiographic quality control, which did not reveal defects in excess of 0.1 mm.

The mechanical properties of Inconel 738 standard alloy and welded joints are shown in Table 1. As follows from Table 1, welded joints obtained using composite welding wires 'E' and 'F' at ambient temperature did not contain cracks and had high mechanical properties. while argon-arc butt welding of the Inconel 738 alloy using standard filler materials without preheating led to intense cracking of the HAZ.

The present invention is described using the most characteristic examples and allows other variations and modifications without deviating from the scope of the invention reflected in the claims.

Claims (22)

1. Composite welding wire for repair by fusion welding of parts of gas turbine engines made of heat-resistant alloys based on nickel, cobalt or iron, containing a core and a deposited and associated surface layer containing boron and / or silicon, characterized in that the total boron content and / or silicon in the composite welding wire is calculated by the expression:

where C _∑ is the total content of boron and / or silicon in the welding wire; D 'is the diameter of the welding wire; C _SL is the content of boron and / or silicon in the surface layer; T is the thickness of the surface layer, while C _∑ is 0.1-10 wt. % 2. The welding wire according to claim 1, characterized in that the total content of boron in it does not exceed 4 wt. % 3. The welding wire according to claim 1, characterized in that the content of boron and / or silicon in the surface layer is 5-95 wt. % 4. The welding wire according to claim 1, characterized in that the surface layer contains 5-50 wt. % boron and / or silicon and an organic binder. 5. The welding wire according to claim 1, characterized in that the content of boron and / or silicon in the surface layer is more than 50 wt. % 6. The welding wire according to claim 1, characterized in that the surface layer is connected to the core by adhesion. 7. The welding wire according to claim 1, characterized in that the surface layer is obtained by sintering in a solid state. 8. The welding wire according to claim 1, characterized in that the surface layer is connected to the core by diffusion. 9. The welding wire according to claim 8, characterized in that it further comprises a transition layer located between the core and the surface layer. 10. The welding wire according to claim 8, characterized in that the surface layer is connected with the core by diffusion of boron. 11. The welding wire according to claim 8, characterized in that the surface layer is connected to the core by diffusion of silicon. 12. The welding wire according to claim 1, characterized in that the core is made of materials selected from nickel-based alloys, heat-resistant nickel alloys, cobalt-based alloys, heat-resistant cobalt alloys, iron-based alloys, heat-resistant iron alloys. 13. The welding wire according to claim 1, characterized in that the core is made of a solid core rod. 14. The welding wire according to claim 1, characterized in that the core is made of a hollow rod. 15. The welding wire according to claim 14, characterized in that the surface layer is an outer surface layer, an inner surface layer or an inner and outer surface layer. 16. The welding wire according to claim 4, characterized in that the organic binder is selected from synthetic or natural acrylic, polyester, epoxy, vinyl-acrylic, vinyl acetate-ethylene, melamine, alkyd resins and oils. 17. The welding wire according to claim 1, characterized in that the surface layer is deposited using a method selected from applying a dye, electrostatic powder spraying, coating with a paste-like mixture, boronation, chemical vapor deposition, physical vapor deposition, electron beam sputtering and electron beam physical vapor deposition.

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